Reactions to the flu can be mild to severe and can lead to death if left untreated. Although most healthy individuals recover from the flu without complications, certain people can have serious complications from the influenza virus. These can include bacterial pneumonia, dehydration, inflammation of chronic medical conditions and sinus infections.

High risk individuals include: those 65 years or older, those who have chronic medical conditions (for example asthma, diabetes, or heart disease), pregnant women, children and infants.